In the art of powered lower extremity exoskeletons, especially where at least two degrees of freedom of the exoskeleton leg are actuated, the main application has been helping persons with complete lower extremity paralysis walk. Several devices have been or are being commercialized for this application. Nevertheless, these devices have generally neglected a larger population of persons with impaired lower extremity function, particularly persons who have survived a stroke. Stroke survivors often exhibit hemiparetic injuries, where one limb is much more severely impaired than the other. While some devices have been designed that provide one powered degree of freedom, such as a powered knee brace, these devices can only help those with more mild injuries, and cannot accommodate as severely impaired a person as a full exoskeleton. Furthermore, these devices result in a significant weight borne by the person on their less impaired leg, which must support the weight of the device when the more impaired leg is in swing; this effect is compounded for heavier devices with two or more degrees of freedom. Finally, the out-of-plane axes in powered lower extremity exoskeletons known in the art are locked, something essential for persons who are completely paralyzed, but that is restrictive for persons who are hemiplegic.
It is seen that there is a need in the market for a versatile rehabilitation exoskeleton that can be used for various handicapped individuals, particularly those with either hemiplegic or paraplegic injuries. This application is concerned with several novel embodiments that overcome these limitations to create a truly versatile and commercially viable general rehabilitation exoskeleton. These several embodiments may be used singly, or combined to greater effect.
Although the devices and concepts disclosed here apply equally to devices that work with a person's upper extremities, lower extremities, or both, the discussion here will be focused on devices used for the lower extremities. The determination of which joints (or degrees of freedom) to actuate, which joints to allow to rotate freely, which joints to passively control (using elastic and/or damping systems), and which joints to fix is made based on the needs of each exoskeleton user. This determination is one of the primary factors limiting the intended user population of an exoskeleton device; for example if a joint is fixed and a user requires the joint to freely rotate the user cannot use the exoskeleton device. Therefore, in order to build an exoskeleton which can serve a greater intended user population it is beneficial if the joint control method can be adjusted to the needs of each exoskeleton user on the fly by the end user.